This article examines the changing practices of the Dutch highest courts, the Hoge Raad and the Afdeling bestuursrechtspraak van de Raad van State, under the influence of globalisation, and the constitutional implications of this development. The increasing intertwinement of legal systems and the increasing possibilities for judges to interact with courts in foreign jurisdictions have stimulated the consideration of foreign legislation and case law in judicial decision-making in individual cases. An empirical study clarifies how the Dutch judges perceive the usefulness of legal comparisons in this context and how foreign law is used in deliberations and judgments. The constitutional implications of the changing practices of the courts are analysed in light of three aspects of the constitutional normative framework for judicial decision-making: the democratic justification of judicial decisions; legal tradition and the nature of cases; and the effectiveness and efficiency of judicial decision-making.